Integrated circuits are typically formed on silicon wafers and oftentimes packaged within a plastic or ceramic body with electrical contacts distributed on the outside of the body to couple power and signals to and from the integrated circuit. The body can protect the fragile integrated circuit and can provide a way to affix the integrated circuit to a supporting structure such as a printed circuit board. One drawback of this approach is that the amount of space required to implement the combined printed circuit board and integrated circuit can be substantial.
Integrated circuits are most often formed, but are not limited to, a silicon-based substrate. Other substrates are possible and can offer different advantages. For example, gallium arsenide can be selected as a substrate and can offer faster circuit switching times yielding a faster overall design. In some designs, an integrated circuit can be thinned after the circuits themselves are formed on the substrate. Thinned integrated circuits can be produced by back-grinding the substrate to reduce an overall thickness. Thinned integrated circuits can require less volume in a design and can, in some designs, offer operational advantages. For example, a thinned integrated circuit can provide different transistor characteristics such as a lower channel resistance.
One way to take advantage of a thinned integrated circuit is to embed the circuit into a substrate such as a printed circuit board. Printed circuit boards (PCBs) can be relatively thick compared to the thinned integrated circuit. For example, a typical PCB can be 0.062 inches thick or thicker, while a thinned integrated circuit can be 50 microns thick. Problems may arise when the thinned integrated circuit is embedded into the PCB. For example, the thinned integrated circuit can suffer warpage or breakage as the PCB undergoes heating/cooling cycles. Furthermore, the thinned integrated circuit can have a different coefficient of thermal expansion than the PCB and can be subject to stresses as the PCB expands and contracts.
Therefore, what is desired is a way to affix a thinned integrated circuit within a PCB substrate that can reduce any extra stress that may be applied to the thinned integrated circuit.